This is an open-label, dose-escalating multi-center trial to determine the safety, tolerability, and pharmacokinetic parameter of 3 doses of DAB389IL-2 in patients with severe psoriasis. The doses were chosen because previous studies have demonstrated that adverse experiences occur more frequently at higher doses and efficacy has been present at all doses. This protocol explores a lower and varied treatment schedule. Efficacy will also be assessed. A total of forty-five patients will be assigned in a dose escalating manner to one of the 3 dose groups (0.5, 1.5, and 5.0 ug/kg/day). Drug is administered 3 days every other week for 8 weeks.